This invention relates to a variable size baby bottle construction. By adjusting the size of the bottle in accordance with the volume of liquid in the bottle it is possible to minimize the possibility of a vacuum developing within the bottle during the course of a baby feeding operation.
The presence of a vacuum condition within a nursing bottle can adversely affect the baby feeding process because the walls of the nipple at the mouth of the bottle then tend to close together so as to restrict the liquid flow. Also, it becomes more difficult for the baby to suck liquid out of the bottle because the vacuum tends to retain liquid within the bottle; the baby has to suck harder to extract the liquid. There have been prior art efforts to eliminate the undesired vacuum condition. U.S. Pat. No. 4,010,861 issued to O. Welten, shows a tubular baby bottle having an air-admission valve in its end wall; a piston is slidably arranged within the tubular bottle to reduce the bottle volume as liquid is sucked out of the bottle. Apparently the intent is to have a freely slidably piston that will respond to pressure differences thereacross by moving to equalize the pressure difference.
U.S. Pat. No. 4,730,744 issued to M. Vinciguerra shows a baby bottle having a spring-biased air valve in its end wall. Vacuum conditions within the bottle tend to open the valve for admitting air into the bottle, thereby tending to overcome the vacuum condition.
U.S. Pat. No. 2,208,360 to F. Deuerme shows a baby bottle having a flexible balloon structure extending from the bottle end wall into the space circumscribed by the bottle. As liquid is extracted from the bottle the negative pressure surrounding the balloon allows atmospheric pressure to expand the balloon into the bottle, thereby returning the liquid space to near atmospheric pressure.
The present invention contemplates a variable size nursing bottle that comprises a tubular sleeve, and a cup-shaped liner slidably telescoped into the sleeve. Circumferential grooves are formed in the sleeve at axially-spaced points therealong. A mating circumferential rib is formed on the liner near its mouth, such that manual motion of the liner into the sleeve enables the rib to have a snap fit in a selected one of the grooves. As the baby extracts liquid from the bottle the mother manually slides the liner into the bottle so that the rib snaps into the next available groove. By periodically noting the vacant space within the bottle the mother can manually reduce the size (length) of the bottle to minimize the vacant space and thereby prevent a vacuum condition from developing within the bottle.